OFDM modulation is a frequency-division multiplexing scheme according to which packets of data are modulated on a large number of closely packed orthogonal sub-carriers. Each sub-carrier is modulated by a conventional modulation scheme, such as QAM (quadrature amplitude modulation) or PSK (phase shift keying). Data is divided into multiple parallel streams, one for each sub-carrier, and transmitted in symbols comprising all of the modulated sub-carriers.
Digital video broadcasting standards such as DVB-T (digital video broadcasting of terrestrial television) and DVB-H (digital video broadcasting to handheld devices) propose the use of OFDM modulation, and can be applied to wired or wireless signal transmission channels, and to various applications such as digital television and audio broadcasting, wireless networking and broadband internet. An advantage of OFDM modulation is its ability to cope with severe channel conditions, such as frequency selective fading.
Demodulating an OFDM signal generally involves performing analogue to digital conversion on the received signal, and then performing a fast Fourier transform (FFT) to convert the signal into the frequency domain. The resulting parallel streams are then processed to extract the data based on an estimation of the channel performed by channel estimation circuitry. However, a problem with existing channel estimation circuitry is that it tends to be inadequate, or complex and demanding on processing resources.